The floating floor was then laid. This consists of 3 layers of MDF. The first layer is a 12.5mm layer. This is nailed directly to the existing floor. Fortunately, the floor in this room is of wood. There is about a 1" airspace between the edge of the floor and the existing walls. The frame of the room stands directly onto the floating floor and does not touch any of the existing structure.
After sealing the floor joints with acoustic sealant, a layer of "Green Glue" is applied and a layer of 15mm MDF is laid on top and secured to the first layer using 20mm screws. The joins in that layer are also sealed. As with the plasterboarding, the sheets are laid so that none of the joins line up, and 2 tubes of Green Glue are applied to each sheet. Another layer of "Green Glue" follows, then the final 12.5mm layer of MDF is secured to the 2nd layer with 20mm screws.
Before too much of the frame was constructed, I took the opportunity to paint any areas of the existing walls that may still be visible after the construction is complete.
The corners of the frame were the first to go up. Two 4"x2" posts were secured together for extra strength at the corners.